How can I tell my Minecraft users which mods they need?

I'm hosting a Minecraft server that gets updated from time to time. I'd like to make it easy for players to know which mods they will need to play without requiring me to communicate with them outside of Minecraft. This info would be good for new players, as well as regular players who need to be informed that a new mod has been added to the server. Currently, if a player is missing a mod in their client, they will see a generic error message.

Is there a way to inform users in-game which mods they will need?

One idea I have is to put a web address on the game screen they see before joining, and then keep that web page updated, but that seems clunky. I know that players can be given the option to download Resource Packs, but as far as I know, this kind of this isn't available for mods.

Players can't join a server if they don't have all the correct mods installed (for Forge at least). I'd put a link in the MOTD, linking to a website like Pastebin, etc., and direct users there. Note that users cannot directly click links in the MOTD, so ideally it should be short.